In general, the fundamental steps in processing color light-sensitive materials are a color-developing step and a desilvering step. In the color-developing step, exposed silver halide is reduced with a color-developing agent to produce silver, and, at the same time, the oxidized color-developing agent in turn reacts with a color former (coupler) to provide a dye image. In the subsequent desilvering step, silver having been produced in the color-developing step is oxidized by the action of an oxidant (called bleaching agent), then dissolved with a silver ion-chelating agent, usually called a fixing agent. After this desilvering step, only a dye image remains in the color light-sensitive material.
The above-described desilvering step is generally conducted in one of two manners: one is conducted using two baths of a bleaching agent-containing bleaching bath and a fixing agent-containing fixing bath; and the other is conducted using a mono-bath containing both a bleaching agent and a fixing agent.
In general, red prussiate, dichromates, ferric chloride, ferric complexes of aminopolycarboxylic acid, persulfates, etc., are known as bleaching agents.
However, red prussiate and dichromates involve environmental problems with respect to cyanide compounds and hexavalent chromium, and require special processing equipment. Ferric chloride involves the problem of production of ferric hydroxide in the subsequent water-washing step and the problem of forming stains, thus involving various difficulties in practical use. Persulfates have the defect that they possess such a weak bleaching power that they require an undesirably long bleaching time. As to this defect, it has been proposed to enhance the bleaching power by using together therewith a bleaching-accelerating agent. However, persulfates furthermore are generally regulated by laws with respect to the prevention of fire hazards; such laws provides for treatment of persulfates as dangerous substances and require various means for storage of persulfates, which are thus generally difficult to use.
Ferric complexes of aminopolycarboxylic acid (particularly ferric complexes of ethylenediaminetetraacetate) are at present most widely used as bleaching agents, since they cause less environmental problems and can be stored with no troubles. However, the bleaching power of the ferric complexes of aminopolycarboxylic acid is not fully satisfactory. When they are used as bleaching agents, the desired objects can be attained to some extent in the case of bleaching or bleach-fixing low-speed silver halide color light-sensitive materials primarily containing a silver chlorobromide emulsion. However, in the case of beleaching or bleach-fixing high speed color-sensitized color light-sensitive materials primarily containing a silver chlorobromoiodide or silver bromoiodide emulsion, particularly color reversal light-sensitive materials and color negative light-sensitive materials for photographic use using high silver content emulsions, there results somewhat insufficient removal of silver, or a long bleaching time is required.
For example, in bleaching color negative light-sensitive materials for photographing use using a bleaching solution containing ferric complex of aminopolycarboxylic acid, bleaching must be conducted for at least four minutes, and, in order to keep bleaching power, complicated control such as control of pH of the bleaching solution and controlled aeration is required. In fact, however, such control often still fails to prevent bleaching deficiencies.
On the other hand, as a means for accelerating the desilvering step, a bleach-fixing solution containing a ferric complex of aminopolycarboxylic acid and a thiosulfate as described in German Pat. No. 866,605 is known. However, when allowed to be copresent with the thiosulfate having a reducing power, the ferric aminopolycarboxylate originally having a weak oxidizing power (bleaching power) undergoes such a serious reduction of oxidizing power that it is extremely difficult to fully remove silver from a high-speed, high-silver content color light-sensitive material intended for photographic use; thus such proposed means is substantially unable to be put into practice. Of course, various attempts have been made to overcome the above-described defects of the bleach-fixing solution. For example, there is a technique of adding an iodide or bromide as described in British Pat. No. 926,569 and Japanese Patent Publication No. 11854/78, and technique of incorporating a ferric complex of aminopolycarboxylic acid in a high concentration with the aid of triethanolamine as described in Japanese Patent Application (OPI) No. 95834/73 (the term "OPI" as used herein means an "unexamined published application"). However, these techniques provide still insufficient effects, and cannot be practically employed with fully satisfactory effects.
As another technique for raising the bleaching power of the ferric complex of aminopolycarboxylic acid, it has been proposed to add various bleaching-accelerating agents to a bleaching bath, a bleach-fixing bath, or a pre-bath thereof.
As the bleaching-accelerating agents, there are illustrated, for example, various mercapto compounds as described in U.S. Pat. No. 3,893,858, British Pat. No. 138,842 and Japanese Patent Application (OPI) No. 141623/78, disulfide bond-containing compounds described in Japanese Patent Application (OPI) No. 95630/78, thiazolidine derivatives as described in Japanese Patent Publication No. 9854/78, isothiourea derivatives as described in Japanese Patent Application (OPI) No. 94927/78, thiourea derivatives as described in Japanese Patent Publication Nos. 8506/70 and 26586/74, etc.
Some of these accelerating agents show a bleaching-accelerating effect to some extent, but the effect is not necessarily sufficient. Thus, they fail to meet the requirement for shortening the processing time.
On the other hand, in silver halide photographic materials, it is well known to provide a layer which absorbs a light of specific wavelength for the purpose of forming a light-absorbing filter, preventing halation, or adjusting sensitivity of light-sensitive emulsions. As is described in T. H. James, The Theory of the Photographic Process, (Macmillan, 1977), pp. 336-337, it is particularly popular to provide a yellow filter layer at a position nearer to a support than a blue-sensitive layer and more distant from the support than other color-sensitive layers.
These colloidal silver particles contained in the yellow filter layer are known to often cause harmful contact fog in adjacent emulsion layers.
Various attempts have been made for preventing this contact fog. For example, Japanese patent Application (OPI) No. 83852/83 describes to add mercaptotetrazole, U.S. Pat. No. 3,206,310 describes to add derivatives of benzothiazole and benzoselenazole, German Patent Publication No. 1,168,251 describes to use triazaindolizine, and Japanese Patent Publication No. 47305/84 describes to use an alkali metal iodide or ammonium iodide. However, in order to obtain sufficient effects, these compounds must be added in large amounts due to their weak ability of preventing contact fog. It has been found that, in the case of using them in large amounts, desilvering properties of the light-sensitive materials are seriously in photographic processing steps, particularly in the bleach-fixing step.
In addition, it has been found that when the contact fog-preventing additives are used in large amounts in the yellow filter layer, light-sensitive materials undergo deterioration of photographic properties after storage, particularly serious reduction in sensitivity of adjacent layers when stored at high temperatures under high humidity.
As is described above, it has been quite difficult to obtain a light-sensitive material which contains a yellow filter of yellow colloidal silver, which shows good desilvering properties and undergoes no contact fog upon being processed in a bleach-fixing solution, and which does not undergo deterioration of photographic properties during storage.
In order to solve the problem of bleaching difficulty in processing a colloidal silver-containing light-sensitive material in a bleaching bath having a weak oxidizing power, it is known to add an aminothiol compound as disclosed in Japanese Patent Application (OPI) No. 83852/83 to the colloidal silver-containing layer or other layer. However, this technique has a photographically serious defect that light-sensitive materials based on this technique undergo fogging of emulsions when stored under the conditions of comparatively high temperature and high humidity. Further, when processed in a bleach-fixing solution containing a ferric complex of aminopolycarboxylic acid and a thiosulfate, light-sensitive materials prepared according to the above-described technique show insufficient desilvering.
Various attempts have been made to use organic dyes in the filter layer in place of colloidal silver. Examples include pyrazolone oxonol dyes as described in British Pat. No. 506,385, barbituric acid oxonol dyes as described in U.S. Pat. No. 3,247,127, azo dyes as described in U.S. Pat. No. 2,390,707, styryl dyes as described in U.S. Pat. No. 2,255,077, hemioxonol dyes as described in British Pat. No. 584,609, merocyanine dyes as described in U.S. Pat. No. 2,493,747, cyanine dyes as described in U.S. Pat. No. 2,843,486, etc.
Desilvering properties of high-speed color light-sensitive materials in bleach-fixing processing can be greatly improved by substituting these dyes for colloidal silver. However, conventional dyes have been quite difficult to put into practice since they do not necessarily meet certain requirements. That is, dyes to be used for such purpose (1) must have good absorption spectrum properties suited for the intended use, (2) must be easily decolored and dissolved away from silver halide photographic materials during photographic development processing and must not remain in the photographic materials after development processing so as to substantially prevent color stain, (3) must not exert detrimental influences on photographic emulsions such as fogging or desensitization, (4) must not diffuse from their own layers to other layers, and (5) must be stable and unchangeable with lapse of time in processing solutions or in silver halide photographic materials.
As is disclosed, for example, in Japanese Patent Application (OPI) No. 40334/77, it is a well known technique to treat silver halide color photographic materials containing dyes which prevent irradiation or halation, in a bleach-fixing solution. However, dyes used for these purposes easily diffuse into other layers. When these dyes diffuse from the layer to which they are added to other layers, they seriously reduce the sensitivity of the other emulsion layers and, in addition, seriously reduce the effect of the filter layer itself.